Apparatus and method for assessing optical quality of gemstones

ABSTRACT

Provided herein is an apparatus for assessing a color characteristic of a gemstone. The apparatus comprises an optically opaque platform for supporting a sample gemstone to be assessed, a daylight-approximating light source to provide uniform illumination to the gemstone, an image capturing component, and a telecentric lens positioned to provide an image of the illuminated gemstone to the image capturing component. Also provided are methods of color analysis based on images collected using such an apparatus.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 15/588,389, filed on May 5, 2017 which in turnclaims priority to U.S. patent application Ser. No. 14/673,776 (U.S.Pat. No. 9,678,018), filed on Mar. 30, 2015 and entitled “APPARATUS ANDMETHOD FOR ASSESSING OPTICAL QUALITY OF GEMSTONES,” which is herebyincorporated by reference herein in its entirety.

FIELD

The apparatus and methods disclosed herein generally relate toassessment of optical qualities of gemstones, in particular cutgemstones. In particular, the apparatus and methods relate to assessmentof color quality of cut diamonds. The apparatus and methods disclosedherein further relate to digital image processing based on colorcomponent analysis.

BACKGROUND

Diamonds and other gemstones are often analyzed and graded by multipletrained and skilled individuals, based upon their visual appearance. Forexample, the foundation of diamond analysis comprises analysis of theFour C's (color, clarity, cut and carat weight), two of which, color andclarity, have been traditionally evaluated by human inspection. Inparticular, a diamond's visual appearance to the human eye under naturalor daylight-approximating light is a primary indicator of the quality ofthe diamond. Accordingly, because diamond quality is substantially basedon human visual perception, analysis and grading requires the exerciseof judgment, the formation of opinions and the ability to draw finedistinctions based on visual comparisons.

A process of inspection and analysis is often time-consuming, involvingmultiple rounds of inspections, measurements and checks by each trainedand experienced individual. The process also involves quality controland may include a variety of non-destructive tests to identifytreatments, fillings or other defects that may affect the quality of aspecimen. Finally, the process includes intensive visual comparison ofthe diamond with a reference set of diamond master stones that serve asa historical standard with respect to diamond color.

Instruments have been created to improve efficiency and to permitgemstone analysis in the absence of trained and experienced individuals.However, even though the performance of these instruments is generallygood, there are issues that continue to cause concerns. Mostsignificantly, there appears to be good evidence that certain stonesconsistently give significantly different results when measured on suchinstruments in comparison to visual grading by experienced humangraders.

What is need are apparatus and methods that can consistently andaccurately approximate gemstone analysis and grading (e.g., color ofdiamonds) by trained and experienced individuals.

SUMMARY

In one aspect, provided herein is an apparatus for assessing a colorcharacteristic of a gemstone. The apparatus comprises an opticallyopaque platform, where the platform has a surface configured forsupporting a gemstone to be assessed; a daylight-approximating lightsource shaped to at least partially enclose the platform, where thelight source is designed to provide uniform diffused illumination to thegemstone on the platform; an image capturing component, where the imagecapturing component is positioned at a predetermined angle relative tothe platform surface that supports the gemstone, and where the imagecapturing component and platform are configured to rotate relative toeach other; and a telecentric lens positioned to provide an image of theilluminated gemstone to the image capturing component.

In another aspect, provided herein is an apparatus for assessing a colorcharacteristic of a gemstone. The apparatus comprises an opticallyopaque platform, where the platform has a surface configured forsupporting a gemstone to be assessed; a daylight-approximating lightsource; a diffuser, where the diffuser and the daylight-approximatinglight source are coupled to provide uniform diffused illumination to thegemstone on the platform; an image capturing component, where the imagecapturing component is positioned at a predetermined angle relative tothe platform surface that supports the gemstone, and wherein the imagecapturing component and platform are configured to rotate relative toeach other; and a telecentric lens positioned to provide an image of theilluminated gemstone to the image capturing component.

In some embodiments, the apparatus further comprises a reflector devicehaving an inner surface that is at least partially spherical andcomprises a reflective material, where the reflector device at leastpartially covers the daylight-approximating light source and platformsurface, and directs light from the light source towards the gemstonepositioned on the platform surface. In some embodiments, the innersurface of the reflector device has a hemispherical shape.

In some embodiments, the telecentric lens comprises an object-spacetelecentric lens, or a double telecentric lens. In some embodiments, thetelecentric lens is a double telecentric lens.

In some embodiments, the platform is configured to rotate about arotational axis that is perpendicular to the surface of the platformwhere the gemstone is supported. In some embodiments, the platform isconfigured to rotate 360 degrees around a rotational axis. In someembodiments, the platform is a flat circular platform, and where therotational axis is through the center of the circular platform.

In some embodiments, the predetermined angle between the image capturingcomponent and the platform surface is between approximately zero andapproximately 45 degrees. In some embodiments, the predetermined anglebetween the image capturing component and the platform surface isbetween approximately 10 and approximately 35 degrees.

In some embodiments, the reflective material on the at least partiallyspherical inner surface of the reflector device is selected from thegroup consisting of polytetrafluoroethylene (PTFE), Spectralon™, bariumsulfate, Gold, Magnesium Oxide, and combinations thereof.

In some embodiments, the platform surface comprises a reflectivematerial. In some embodiments, the platform surface comprises a diffusereflective material. In some embodiments, the platform surface comprisesa white diffuse reflective material. In some embodiments, the platformsurface comprises a Teflon™ material.

In some embodiments, the platform is made of a material selected fromthe group consisting of polytetrafluoroethylene (PTFE), Spectralon™,barium sulfate, Gold, Magnesium Oxide, and combinations thereof.

In some embodiments, the daylight-approximating light source isconfigured as a ring light surrounding the platform surface. In someembodiments, the daylight-approximating light source is selected fromthe group consisting of one or more halogen lamps with a color balancingfilter, multiple light emitting diodes arranged in a ring-like structuresurrounding the platform surface, fluorescence lamp, Xe lamp, Tungstenlamp, metal halide lamp, laser-induced white light (LDLS), andcombinations thereof.

In some embodiments, the image capturing component is selected from thegroup consisting of a color camera, a CCD camera, and one or more CMOSsensor arrays.

In some embodiments, image capturing component captures a plurality ofcolor images of the illuminated gemstone, each taken when the imagecapturing component and the platform surface are at a different relativerotational position.

In some embodiments, the apparatus further comprises a computer readablemedium for storing the images collected by the image capturingcomponent. In some embodiments, where the color characteristic of thegemstone is a color grade.

In one aspect, provided herein is a method of assessing a colorcharacteristic of a sample gemstone. The method comprises the steps of(i) determining a proportion or shape characteristic of a samplegemstone based on a plurality of color images, where each image of theplurality of color images includes a full image of the sample gemstone,is taken at a unique image angle, and comprises a plurality of pixels;(ii) selecting a defined area corresponding to the proportion or shapecharacteristic for further color analysis, where the defined area iswithin the full image of the sample gemstone in each image of theplurality of color images; (iii) quantifying individual color componentsin each pixel in the defined area in each image of the plurality ofcolor images, thereby converting values for individual color componentsto one or more parameters representing the color characteristic of eachpixel; (iv) determining an average value for each of the one or moreparameters for all pixels in the defined area in all images of theplurality of color image; (v) calculating one or more color scores of asample gemstone based on the average values of the one or moreparameters of all pixels in the defined area in all images of theplurality of color images; and (vi) assessing the color characteristicof the sample gemstone by comparing the one or more color scores tovalues of corresponding color scores of one or more control gemstonesclassified to be in the pre-determined category, thereby assigning acolor grade to the sample gemstone.

In some embodiments, the sample gemstone is a diamond.

In some embodiments, the proportion or shape characteristic of thesample gemstone is determined using outline masks created based on theplurality of color images, wherein each outline mask has an open areacorresponding to the full image of the sample gemstone in each image inthe plurality of color images.

In some embodiments, each outline mask has a width and a height. In someembodiments, the proportion or shape characteristic iswidth_(max)/width_(min), wherein width_(max) is the maximum widthidentified for the outline masks and width_(min) is the minimum widthdiamond width identified for the outline masks.

In some embodiments, the proportion or shape characteristic is(height/width)_(min), wherein (height/width)_(min) is the minimum aspectratio identified for the outline masks.

In some embodiments, the defined area is selected using a virtual maskhaving an open area that corresponds to a portion of the open area inthe corresponding outline mask. In some embodiments, the open area ofthe virtual mask corresponds to 30% to 100% of the total area of theopen area of the outline mask.

In some embodiments, the individual color components comprise the colorsred (R), green (G) and blue (B).

In some embodiments, average values for one individual color componentare calculated by averaging the values corresponding to the individualcolor component of each pixel in the defined area.

In some embodiments, the method further comprises the step of collectingthe plurality of color images of the sample gemstone using an imagecapturing component at uniquely different image angles, where an imageangle defines the relative angular position between the image capturingcomponent and a predetermined reference position on a platform surfaceupon which the sample gemstone is positioned.

In some embodiments, the image capturing component receives each imageof the illuminated gemstone in the plurality of color images from atelecentric lens. In some embodiments, the telecentric lens comprises anobject-space telecentric lens, or a double telecentric lens. In someembodiments, the telecentric lens is a double telecentric lens.

In some embodiments, the method of color assessment further comprises astep of collecting a new plurality of color images of the samplegemstone using the image capturing component at the image angle and thepredetermined reference position on the platform surface. In suchembodiments, there is a time gap between the time when the plurality ofcolor images is collected and the time when the new plurality of colorimages is collected.

In some embodiments, a new color grade is assigned to the samplegemstone based on the new plurality of color images by applying steps(i) through (vi). The new color grade and the previously determinedcolor grade are then compared to evaluate color change over the timegap.

In some embodiments, the time gap is between 2 minutes and 2 hours.

It will be understood that any of the embodiments disclosed herein canbe applied, alone or in combination, to all aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Those of skill in the art will understand that the drawings, describedbelow, are for illustrative purposes only. The drawings are not intendedto limit the scope of the present teachings in any way.

FIG. 1 depicts an exemplary embodiment of a gemstone optical assessmentsystem including an optical unit, a gemstone evaluation unit.

FIG. 2A depicts an exemplary schematic embodiment of a gemstone opticalassessment system in a closed configuration.

FIG. 2B depicts an exemplary schematic embodiment of a gemstone opticalassessment system in an opened configuration.

FIG. 3 depicts an exemplary embodiment of a sample platform withsurrounding ring light illumination.

FIG. 4 depicts an exemplary schematic illustrating image view angle andimage rotational angle.

FIG. 5A depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 5B depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 5C depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 5D depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 6A depicts an exemplary embodiment of a connector module forlinking a gemstone evaluation unit and an optic unit.

FIG. 6B depicts an exemplary embodiment of a connector module forlinking a gemstone evaluation unit and an optic unit.

FIG. 6C depicts an exemplary embodiment of a connector module forlinking a gemstone evaluation unit and an optic unit.

FIG. 7A depicts an exemplary embodiment before an outline mask isapplied.

FIG. 7B depicts an exemplary embodiment after an outline mask is appliedto highlight the width and height of a diamond.

FIG. 8 depicts an exemplary organization of a computer system.

FIG. 9A depicts an exemplary process for a data collection and analysis.

FIG. 9B depicts an exemplary process for a data collection and analysis.

FIG. 10 depicts an exemplary analytical process.

FIG. 11A depicts an exemplary classification process.

FIG. 11B depicts an exemplary re-classification process.

FIG. 12A depicts exemplary color grading calculations.

FIG. 12B depicts exemplary color grading results.

FIG. 13 depicts exemplary color grading results.

FIG. 14A depicts exemplary color grading results.

FIG. 14B depicts exemplary color grading calculations.

FIG. 15 depicts exemplary color grading results.

DETAILED DESCRIPTION

Unless otherwise noted, terms are to be understood according toconventional usage by those of ordinary skill in the relevant art. Forillustration purposes, diamonds are used as the representativegemstones. One of skill in the art would understand that theapparatuses, systems and methods disclosed herein are applicable to alltypes of gemstones capable of emitting fluorescence upon UV exposure.Systems and methods for fluorescence grading based on similarapparatuses are disclosed in U.S. patent application Ser. No.14/673,780, filed on Mar. 30, 2015, and entitled “APPARATUS AND METHODFOR ASSESSING FLUORESCENCE GRADING OF GEMSTONES” and filed concurrentlyherewith, which is hereby incorporated by reference herein in itsentirety.

The currently available color grade instrument works quite well forcolor grading of certain type of gemstones; for example, regular roundbrilliant cut (RBC) diamond stones that are in the range of D-Z colorgrade of cape yellow hue. However, similar success is not observed forgemstones with irregular shapes, cut, sizes, or uncommon colors. Inparticular, the current instrument cannot provide consistent andreproducible color grade to brown stones, off-color stones (pink,yellowish-green, green and blue) and fancy shape cut stones (Step Cuts,Hearts, Marquises, Ovals, Pears, Triangles, Princess and other cutsrather than RBC).

Several critical issues are to be solved before better and morepractical color grading instrument is built. For example, currentinstrument uses optical fiber to detect the light coming out of diamond.As a consequence, color grade is affected significantly by diamondposition relative to the optical axis of fiber: getting reproducibleresults is difficult because the system set up requires that a testgemstone must be in exactly the same position. Further, color grade issignificantly affected by the small change of distance between fiberedge and diamond and also the angle of optical fiber. This also leads tothe inconsistent color grade among different devices since optical setupis extremely difficult and its alignment is easily changed during dailyoperation.

In order to overcome the existing issues, an improved color gradeinstrument as disclosed herein as the following characteristics: (1) toprovide consistent and reproducible color grade to diamonds withdifferent hue range (brown, pink, green and blue); (2) to provideconsistent and reproducible color grade to any kinds of fancy shapediamonds; (3) to provide consistent and reproducible color grade witheasy and quick operation (e.g., operators do not need to put stones inthe same position); and (4) to be simple so that optical setup is easyand robust enough to daily operation.

In one aspect, provided herein is an improved color grading apparatusfor color assessment of gemstones such as cut diamonds. The apparatus issuitable for grading any gemstones such as cut diamonds, includinggemstones of irregular shapes, sizes and colors. For example, theapparatus can grade a gemstone with one or more curved edges, a gemstonewith one or more straight edges, a gemstone with a combination ofstraight and curved edges, a gemstone with high or low depth, a stonewith unusual shape such as marquise, emerald, and cushion, as well as astone with unusual colors such as pink, blue, brown, green, yellow andetc. An exemplary apparatus 100 is illustrated in FIG. 1, which includesbut is not limited to, for example, a gemstone evaluation component 10,a light source 20, a telecentric lens 30, and an image capturingcomponent 40.

Based on functionality, the components of an apparatus disclosed hereincan be divided into two main units: a gemstone presentation unit and anoptical unit. The gemstone presentation unit provides uniformillumination to gemstones being analyzed and the optical unit capturesimages of gemstones being presented.

Additionally and not depicted in FIG. 1, an exemplary apparatus furthercomprises a computer processing unit for analyzing information collectedby the image capturing component.

As illustrated in FIG. 1, an exemplary gemstone presentation unit inturn comprises at least two parts: gemstone evaluation component 10 anda light source 20. The gemstone evaluation component is where a gemstoneis presented. As depicted in FIGS. 2A and 2B, the gemstone evaluationcomponent has a closed and an open configuration. In the closedconfiguration (see, e.g., FIG. 2A), a gemstone subject to analysis iscompletely concealed and not visible from an observer. In someembodiments, in order to avoid the inconsistencies caused byinterference from other light such as ambient light, gemstone evaluationcomponent is isolated and closed system from which ambient light orother light is excluded. The gemstone evaluation component and opticunit are joined in a complementary manner such that ambient light orother light is excluded from a concealed sample chamber within which asample gemstone is housed.

Under the closed configuration, image information concerning thegemstone being analyzed is received and captured by the optical unit,which comprises a telecentric lens 30 and an image capturing device 40(e.g., a camera).

In the open configuration (see, e.g., FIG. 2B), no image information iscollected. Instead, the gemstone subject to analysis is exposed to anobserver. In the open configuration, the gemstone presentation unit isrevealed to have two parts: a bottom presentation component 50 and a topreflector component 60. In some embodiments, as illustrated in FIG. 2B,the top reflector component is mounted on movable side tracks. When thetop reflector is moved on these tracks away from the optical unit, thebottom presentation component 50 is exposed. As shown in FIG. 2B, theshape and design of the opening of the top reflector component 60 iscomplementary to the shape and design of the optical connector module(e.g., element 70 in FIG. 2B) of the optical unit. In some embodiments,the optical connector module is a lens hood to which the telecentriclens 30 is attached.

An exemplary bottom presentation component 50 is illustrated in FIG. 3.A circular white reflective platform 510 functions as the base on whicha sample gemstone 520 is placed. A concentric circular ring light 530 isplaced outside the circular platform such that the platform iscompletely enclosed within ring light 530.

Platform 510, also referred to as a stage or sample stage, is criticalfor the system disclosed herein. Importantly, it provides support to agemstone that is being analyzed. In some embodiments, the top surface ofthe platform is a horizontal and flat. In addition, it functions as astage for data collection by telecentric lens 30 and image capturingdevice 40 and subsequent analysis. In order to achieve data consistency,telecentric lens 30 is positioned at a first pre-determined anglerelative to the top surface of platform 510. In some embodiments, imagecapturing device 40 is positioned at positioned at a secondpre-determined angle relative to the top surface of platform 510. Insome embodiments, the first and second pre-determined angles are thesame and it has been optimized for data collection. In some embodiments,the first and second pre-determined angles are different, but each hasbeen optimized for data collection. The first and second pre-determinedangles can be referred to as the image or camera view angle.

An exemplary illustration of the relative configuration of the topsurface of platform 510 to the optical unit (e.g., telecentric lens 30and camera 40) is depicted in FIG. 4. Here, the optical unit, includingboth telecentric lens 30 and image capturing device 40, is positioned ata pre-determined angle (alpha) relative to the platform surface.

In some embodiments, the circular reflective platform is rotatable. Forexample, the platform is mounted on or connected with a rotor. Inpreferred embodiments, a gemstone being subjected to analysis is placedat the center of the platform surface, as illustrated in FIG. 3. Theplatform is then rotated in relation to the optical unit such thatimages of the gemstone at different angles are collected by the imagecapturing device.

In some embodiment, the platform surface is rotated around a rotationalaxis that goes through the center of origin of the circular platformsurface and is perpendicular to the platform surface; see, for example,axis Zz depicted in FIG. 4.

In some embodiments, the platform is rotated in relation to the opticalunit at set angular variations. The magnitude of the angular variationsdetermines the extent of data collection; for example, how many imageswill be collection of the gemstone. For example, if the platform isrotated at an angular variation of 12 degree, a full rotation will allow30 images of the gemstone to be collected. The angular variation can beset at any value to facilitate data collection and analysis. Forexample, the platform can be rotated at an angular variation of 0.5degree or smaller, 1 degree or smaller, 1.5 degree or smaller, 2 degreeor smaller, 3 degree or smaller, 4 degree or smaller, 5 degree orsmaller, 6 degree or smaller, 7 degree or smaller, 8 degree or smaller,9 degree or smaller, 10 degree or smaller, 12 degree or smaller, 15degree or smaller, 18 degree or smaller, 20 degree or smaller, 24 degreeor smaller, 30 degree or smaller, 45 degree or smaller, 60 degree orsmaller, 90 degree or smaller, 120 degree or smaller, 150 degree orsmaller, or 180 degree or smaller. It will be understood that theangular rotational variation can be set at any number. It will also beunderstood that the platform can be rotated for a total rotational angleof any value, not limited to a 360 degree full rotation. In someembodiments, data (e.g., color images) are collection for a rotationless than a 360 degree full rotation. In some embodiments, data (e.g.,color images) are collection for a rotation more than a 360 degree fullrotation.

In some embodiments, the platform or a portion thereof (e.g., the topsurface) is coated with a reflective surface to achieve reflectivity. Insome embodiments, the platform or a portion thereof (e.g., the topsurface) comprises a reflective material. In some embodiments, theplatform or a portion thereof (e.g., the top surface) is made of areflective material. In some embodiments, the reflective material is awhite reflective material. In some embodiments, the reflective materialis Teflon™ material. In some embodiments, the reflective materialincludes but is not limited to polytetrafluoroethylene (PTFE),Spectralon™, barium sulfate, Gold, Magnesium Oxide, or combinationsthereof.

Preferably, the rotatable platform is round and larger than the size ofany sample gemstone to be analyzed. In some embodiments, the platform ishorizontal and remains horizontal while it is being rotated.

In some embodiments, the height of the platform is fixed. In someembodiments, the height of the platform is adjusted, either manually orvia the control of a computer program. Preferably, the platform can beraised or lowered by via the control of a computer program run by thecomputer unit.

In some embodiments, the platform is flat. In some embodiments, thecenter area on which the gemstone sample is positioned is flat and themore peripheral area on the platform is not flat. The entire platformadopts the confirmation of a flatted dome-like structure.

In some embodiments, the relative position between the platform and theillumination source can be adjusted. For example, the illuminationsource can be moved closer or further away from the platform.

A platform can be made of any rigid and non-transparent material such asmetal, wood, dark glass, plastic or other rigid polymeric material. Insome embodiments, the platform and/or area surrounding the platform arecoated with non-reflective or low-reflective material.

In the broadest sense, a light source 20 includes but is not limited tothe source for generating light, one or more filters, elements forconducting the generated light, and a component (e.g., a circular ringlight) that emit the light as illumination. As disclosed herein, thesource for generating light is sometimes referred to as light source.One of skill in the art would understand that the illumination componentis also a part of the light source.

In some embodiments, the light generating source is separated from theultimate illumination component, for example, it is connected with acircular ring light (e.g., by light transmission cables) to provide thesource of illumination. In some embodiments, the light generating sourceitself is the circular ring light. Here, elements that can generateillumination is arranged into a circular or near circular shape. In theembodiment depicted in FIG. 3, a circular ring light 530 providesillumination to the sample gemstone.

In preferred embodiments, the light source is a daylight-approximatinglight source. Exemplary daylight-approximating light source includes butis not limited to one or more halogen lamps with a color balancingfilter, multiple light emitting diodes arranged in a ring-like structuresurrounding the platform surface, fluorescence lamp, Xe lamp, Tungstenlamp, metal halide lamp, laser-induced white light (LDLS), orcombinations thereof.

In some embodiments, cables such as gooseneck light guide, flexiblelight guide, each containing one or more branches are used to connectedthe ring light with the light source.

The illumination source can adopt any shape and size that are suitablefor the optical analysis of a sample gemstone. For example, theillumination source can be a point light, a round light, a ring light,an oval light, a triangular light, a square light, or any other lightwith suitable size and shape. In some embodiments, the lightilluminating source is ring-like or circular in shape, with a diameterthat is larger than that of a circular platform.

In some embodiments, the circular ring light is equipped with one ormore light source. For example, the ring light can be a circularfluorescent light bulb. In some embodiments, the ring light has embeddedwithin one or more light emitting diodes (LEDs). In such embodiments,light source and circular ring lights can be used interchangeably. Insome embodiments, a light source is positioned above a gemstone; forexample, a lamp or one or more LEDs are placed above the platform. Thegemstone subject to analysis is irradiated via an optical diffuser asdescribed in U.S. Pat. No. 6,473,164, which is hereby incorporated byreference herein in its entirety.

An illumination component provides the input light under which thesample gemstone can be analyzed. In some embodiments a form ofillumination is chosen that it is a reasonably good approximation to thetheoretical CIE standard illuminant D65.

A modular approach to the design of the apparatus has been adopted toprovide experimental flexibility. This also applies to the ways in whichgemstones such diamonds are illuminated. For stones mounted table-down,two illumination configurations have been used: from the rear and fromoverhead.

In some embodiments, in order for light rays to contain informationabout the color of a diamond, they must have passed through the stone.No color information is contained in rays that are reflected off thefront facets of the diamond. At first sight, therefore, it would appearsensible to provide illumination substantially from the rear of thediamond while avoiding illuminating the front of the diamond.

In some embodiments, the uneven brightness of the image can be avoidedif the diffuse illumination comes from above the diamond and from a muchlarger range of azimuthal angles. Top illumination has the advantage ofmuch more closely emulating the illumination geometry used in visualgrading but, of course, includes front-surface reflections.

In order to achieve this top illumination geometry, a new illuminatorbase plate was manufactured to accommodate a fiber-optic annular“ring-light.” Preferably, the diameter of the fiber-optic ring light islarger than the diameter of the platform upon which the gemstone isplaced. For example, the diameter of a fiber-optic ring light is 10 mmor larger, 16 mm or larger, 20 mm or larger, 24 mm or larger, 28 mm orlarger, 32 mm or larger, 40 mm or larger, 44 mm or larger, 50 mm orlarger, 56 mm or larger, 60 mm or larger, 64 mm or larger, 70 mm orlarger, 80 mm or larger, 90 mm or larger, or 100 mm or larger. One ofskill in the art would understand that the diameter of the ring lightcan be adjusted to optimize measurements of a particular gemstonesample. In some embodiments, the diameter of a fiber-optic ring light is58 mm.

In some embodiments, the light source is positioned at the platformsurface level or slightly below. In some embodiments, the light sourceis positioned above the platform surface. In some embodiments, theintensity of an illumination source can be adjusted to optimize imagecollection.

As shown in FIGS. 2A and 2B, a top reflector module can be moved overthe area where a sample gemstone is positioned. In the closedconfiguration shown in FIG. 2A, the internal cavity of the top reflectormodule functions as a sealed and isolated sample chamber in which thesample gemstone is analyzed in a controlled environment. For example,ambient light or other light is excluded from the chamber. A user canadjust light intensity within the chamber to optimize data collection.In some embodiments, data collected include color images of the gemstoneviewed from different angles.

FIGS. 5A through 5D illustrate an exemplary embodiment of the topreflector component 60. Overall, the top reflector has an externalmorphology that resembles that of a short cylinder, except that aportion of the cylinder is carved away to form a curved slope (see, forexample, element 610 in FIGS. 5B and 5D). A portion of the slope isremoved to allow access to the inside of the reflector component. Forexample, as shown in FIGS. 5A-5D, the lower portion of slope 610 isremoved to form an opening 620. In some embodiments, the top port ofopening 620 is circular in design; for example with a diameter throughwhich a lens from the optical unit is fitted. In some embodiments, thediameter is the same as that of the telecentric lens to prevent ambientlight or other light from entering the inside of the reflector. In someembodiments, the diameter is slightly larger than that of thetelecentric lens such that an adaptor module is needed to preventambient light or other light from entering the inside of the reflector.

Inside of top reflector module 60 is reflective surface 630. Thisinternal reflective surface is at least partially hemispherical. In someembodiments, the internal reflective surface adopts a shape that is partof the involute of a circle having a radius R. In preferred embodiments,the circle is located at the center of the platform surface and has adiameter that is larger than the sizes of the gemstones being analyzed.The shape of the involute surface is described based on the followingequations:x=R(cos θ+θ sin θ)y=R(sin θ−θ cos θ),where R is the radius of the circle and θ is an angle parameter inradians. The involute surface will reflect light toward the centercircular region such that illumination of the gemstone being analyzed isoptimized.

In some embodiments, the reflective surface 630 or a portion thereofcomprises a reflective material. In some embodiments, the reflectivesurface 630 or a portion thereof is made of a reflective material. Insome embodiments, the reflective material is a white reflectivematerial. In some embodiments, the reflective material is Teflon™material. In some embodiments, the reflective material includes but isnot limited to polytetrafluoroethylene (PTFE), Spectralon™, bariumsulfate, Gold, Magnesium Oxide, or combinations thereof. Additionalreflective coating materials include but are not limited to a zinc salt(zinc sulfide), titanium dioxide, silicon dioxide, a magnesium salt(magnesium fluoride, magnesium sulfide).

As illustrated in FIG. 2B, an optical connector module 70 links thegemstone evaluation unit with the optical unit to permit data collectionby image capturing device 40, whiling at the same time preventingambient light or other light from entering the gemstone evaluation unitand interfering with data measurements.

FIGS. 6A to 6C provide more detailed illustrations of an exemplaryembodiment of an optical connector module. In this case, the connectoris a lens hood for receiving the telecentric lens 30. On the side incontact with the telecentric lens, the lens hood has a flat surface 710.On the opposite side which contacts the reflector, the lens hood has acurved internal surface 720. In some embodiments, the curved surface 720has a shape complementary to the curved surface 610 on the reflector.

Additionally, the connector also has an opening 730; see, FIGS. 6A, 6B,and 6C. In some embodiments, opening 730 has a configuration thataccommodates the telecentric lens while preventing interference fromambient light or other light.

In some embodiments, internal surface 720 or a portion thereof comprisesa reflective material. In some embodiments, internal surface 720 or aportion thereof is made of a reflective material. In some embodiments,the reflective material is a white reflective material. In someembodiments, the reflective material is Teflon™ material. In someembodiments, the reflective material includes but is not limited topolytetrafluoroethylene (PTFE), Spectralon™ barium sulfate, Gold,Magnesium Oxide, or combinations thereof. Additional reflective coatingmaterials include but are not limited to a zinc salt (zinc sulfide),titanium dioxide, silicon dioxide, a magnesium salt (magnesium fluoride,magnesium sulfide).

A lens hood or other optical connector module allows integration of twodifferent functional components. It is designed such that no or verylittle ambient light or other light enters the sample chamber. In someembodiments, additional elements such as a sealing tape can be used toexclude ambient light or other light.

Another main functional component of the system is an optical unitthrough which data of the gemstones being analyzed. The optical unitprovides a sample chamber that enables the collection of a visible-lightspectrum from an area containing a sample gemstone while excluding lightfrom outside the chamber. Optical measurement such as an image iscaptured of the area containing the sample gemstone and, possiblythrough analysis of the detailed structure of the images, to providesome insight into the reasons for certain stones that previously hadanomalous grading results.

Exemplary embodiments disclosed herein include but are not limited totwo important functional modules in the optical unit a telecentric lens30 and an image capturing component 40 such as a color camera. One ofskill in the art would understand that additional components can bepresent to facilitate data collection.

A telecentric lens is used to provide an image of the illuminatedgemstone to the image capturing component. Telecentricity refers to aunique optical property where the chief rays (oblique rays which passthrough the center of the aperture stop) through a certain lens designare collimated and parallel to the optical axis in image and/or objectspace. A telecentric lens is a compound lens which has its entrance orexit pupil at infinity. Advantageously, a telecentric lens providesconstant magnification (object size does not change) over a range ofworking distances, virtually eliminating perspective angle error. Formany applications, this means that object movement does not affect imagemagnification, allowing for highly accurate measurements in gaugingapplications. This level of accuracy and repeatability cannot beobtained with standard lenses. The simplest way to make a lenstelecentric is to put the aperture stop at one of the lens's focalpoints.

There are three types of telecentric lens. An entrance pupil at infinitymakes a lens object-space telecentric. An exit pupil at infinity makesthe lens image-space telecentric. If both pupils are at infinity, thelens is double telecentric.

Telecentric lens with high depth of field are used in the systemdisclosed herein. In some embodiments, a telecentric lens used is anobject-space telecentric lens. In some embodiments, a telecentric lensis a double telecentric lens. In preferred embodiments, zoom should befixed for all images collection for a given gemstone stone to furtherensure consistency.

Advantageously, the present apparatus and system do not require that thesample gemstone be placed at the center of the platform surface. Inaddition, a telecentric lens does not discriminate the size of thesample gemstones. The same telecentric lens can be used to collectionimages for a very small gemstone and a significantly larger gemstone.

The optical unit further comprises an image capture component or adetector such as a digital camera.

In some embodiments, image capturing component 40 comprises one or morephotodiode arrays of a CCD (charge coupled device). In some embodiments,image capturing component 40 comprises one or more CMOS (complementarymetal oxide semiconductor) image sensors. In some embodiments, imagecapturing component 40 comprises a combination of one or more photodiodearrays with CMOS sensors. In some embodiments, image capturing component40 is a CCD digital camera, such as a color digital camera. When imagesfrom different color grading apparatuses are analyzed, more consistentresults can be obtained if the apparatuses use the same type ofdetection methods; for example, all CCD arrays, all CMOS sensors, or thesame combination of both types.

For more accurate analytical results, the resolution limit for thedigital images collected is 600 pixel×400 pixel or above. In someembodiments, each pixel has an 8-bit value (e.g., 0 to 255) for eachcolor component. The Analog to Digital Converter (ADC) of the digitalcamera is 8-bit or above in order to efficiently process the informationembedded in the pixels without little or no loss of image quality. Insome embodiments, the ADC is 10-bit or above according to the dynamicrange of image capturing component. In some embodiments, the ADC isbetween 10-bit and 14-bit.

In some embodiments, the color components in a pixel include but notlimited to red (R), green (G) and blue (B). In some embodiments, thecolor components in a pixel include but not limited to) cyan (C),magenta (M), yellow (Y), and key (black or B). In some embodiments, thecolor components in a pixel include but not limited to red (R), yellow(Y) and blue (B).

In some embodiments, a multi-band camera or hyper spectrum camera isused for capturing images. A multi-band camera is capable to detectlight in the infrared (IR) and far-infrared (FIR) ranges in addition tothat of the visible spectrum. For example, a multi spectral cameraenables a user to better discriminate targets from both background anddecoys by blending color images with information from the IR band.Images obtained from such a system penetrate darkness, camouflage, smokeand clutter better than either visible or IR images could alone.

A hyper spectrum camera, like other spectral imaging devices, collectsand processes information from across the electromagnetic spectrum, butbeyond the visible range. The goal of hyperspectral imaging is to obtainthe spectrum for each pixel in the image of a scene. Much as the humaneye sees visible light in three bands (red, green, and blue), spectralimaging divides the spectrum into many more bands. Hyperspectral imagingtechnique divides images into bands that can be extended beyond thevisible range. In hyperspectral imaging, the recorded spectra have finewavelength resolution and cover a wide range of wavelengths, allowing auser to find objects, identify material or detect process that arepreviously impossible when using regular imaging techniques.

In one aspect, imaging techniques are used to approximate or simulatethe visual perception of human eyes. For example, in some cases, aspectrum function ƒ(x) is used to describe the perception (e.g., colorperception) of human eyes. It is understood that human eyes are morereceptive to light in certain wavelengths or wavelength ranges whilebeing less receptive to other wavelengths or wavelength ranges. Inpractice, the effects can be approximated or simulated by using multiplefilters to weaken or eliminate the non-receptive light. In someembodiments, multiple images are taken for each image view angle andimage rotational angle, where each image is taken using a band-passfilter. This way, gemstone images with multiple spectrum regions can beobtained. These images are then combined to form a composite image thatsimulate the visual perception by human eyes. It will be understood thatusing only one band filter will unlikely match the effects described inspectrum function ƒ(x) and more band-filters will allow fine tuning andeventual close matching the described visual effects.

Image view angle: As depicted in FIG. 4, an image capturing device (ortelecentric lens 30 or both) is positioned at a pre-determined angle(alpha, also referred to as the image view angle) relative to theplatform surface. In some embodiments, the image view angle is 65 degreeor smaller, 60 degree or smaller, 56 degree or smaller, 52 degree orsmaller, 50 degree or smaller, 48 degree or smaller, 46 degree orsmaller, 44 degree or smaller, 42 degree or smaller, 40 degree orsmaller, 39 degree or smaller, 38 degree or smaller, 37 degree orsmaller, 36 degree or smaller, 35 degree or smaller, 34 degree orsmaller, 33 degree or smaller, 32 degree or smaller, 31 degree orsmaller, 30 degree or smaller, 29 degree or smaller, 28 degree orsmaller, 27 degree or smaller, 26 degree or smaller, 25 degree orsmaller, 24 degree or smaller, 23 degree or smaller, 22 degree orsmaller, 21 degree or smaller, 20 degree or smaller, 19 degree orsmaller, 18 degree or smaller, 17 degree or smaller, 16 degree orsmaller, 15 degree or smaller, 14 degree or smaller, 13 degree orsmaller, 12 degree or smaller, 11 degree or smaller, or 10 degree orsmaller. In some embodiments, the image view angle is between about 10degree and about 45 degree. For consistency, the image view angle for agiven gemstone will remain constant when images are collected.

Image rotational angle: Also as illustrated in FIG. 4, the relativerotational position between the imaging capturing component and apre-defined location on the platform (e.g., point 540) can be describedby an image rotational angle beta. For example, the image capturingcomponent and the platform surface can be rotated relative to each othersuch that the image rotational angle is varied by a set angularvariation between consecutive images. For example, the angular variationbetween two consecutive images can be 0.5 degree or smaller, 1 degree orsmaller, 1.5 degree or smaller, 2 degree or smaller, 3 degree orsmaller, 4 degree or smaller, 5 degree or smaller, 6 degree or smaller,7 degree or smaller, 8 degree or smaller, 9 degree or smaller, 10 degreeor smaller, 12 degree or smaller, 15 degree or smaller, 18 degree orsmaller, 20 degree or smaller, 24 degree or smaller, 30 degree orsmaller, 45 degree or smaller, 60 degree or smaller, 90 degree orsmaller, or 180 degree or smaller. It will be understood that theangular rotational variation can be set at any number.

It will also be understood that the platform and image capturingcomponent can be rotated relative to each other for a total rotationalangle of any value, not limited to a 360 degree full rotation. In someembodiments, data (e.g., color images) are collection for a rotationless than a 360 degree full rotation. In some embodiments, data (e.g.,color images) are collection for a rotation more than a 360 degree fullrotation.

It is possible to change angular rotational variation when collecting aset of images for the same sample gemstone. For example, the angulardifferent between image 1 and image 2 can be 5 degrees, but thedifferent between image 2 and 3 can be 10 degrees. In preferredembodiments, angular difference between consecutive images remainsconstant within the same set of images for the same sample gemstone. Insome embodiments, only one set of images is collection for a givensample gemstone. In some embodiments, multiple sets of images arecollected for the same gemstone where angular differences remainconstant within each set but are different from each other. For example,a first set of images is collected by varying the rational image angleby 12 degree for consecutive images, while a second set of images iscollected by varying the rational image angle by 18 degree forconsecutive images.

The number of images collected for a given sample gemstone variesdepending on the characteristics of the gemstone. Exemplarycharacteristics include but are not limited to shape, cut, size, colorand etc.

Visible-light spectra from an area on the platform surface that containsthe sample gemstone is selectively collected. In some embodiments,multiple color images are collected for each gemstone. In someembodiments, multiple non-color images are collected for each gemstone.Color images are advantageous for determining, for example, the colorgrade of a cut diamond.

In some embodiments, the image capturing component or detector is aNikon Digital Sight 5.0 megapixel color CCD camera head, DS-Fil. Thishas a high spatial resolution with a field of view of 2560×1920 pixelsand a reasonably high acquisition rate of 12 frames per second. In someembodiments, alternative cameras with alternative resolution are used.

In some embodiments, the image capturing component or detector is a CCDcamera that has same filter function as human eyes and also higher colorresolution, such as Konica Minolta: CA-2500. In some embodiments, thedetector measures photo-luminescence by using microcomputer control.

In some embodiments, as will be discussed further in sections thatfollow, images captured by the CCD camera will be processed in order toidentify regions of differing intensity of color. Furthermore,colorimetric calculations can be performed on these different areasusing the red, green and blue signals from the camera pixels. In someembodiment, such calculations will be sufficiently accurate to give acolor grade. In some embodiment, such calculations will be sufficientlyaccurate to provide a color distribution across the diamond and thecomparison of these color calculations with that obtained from themeasured spectrum can help identify diamonds that are likely to giveanomalous results.

In some embodiments, the color grade is determined based on color valuescomputed from the entire sample gemstone. In some embodiments, the colorgrade is determined based on color values computed from selected area ofthe sample gemstone.

Resolution and capacity of a detector can be determined by the numberand size of the pixel in the detector arrays. In general, the spatialresolution of the digital image is limited by the pixel size.Unfortunately while reducing pixel size improves spatial resolution thiscomes at the expense of signal to noise ratio (SNR or signal/noiseratio). In particular, signal-to-noise ratio is improved when the imagesensor pixel size is increased or when the image sensor is cooled. Atthe same time, size of the image sensor is increased if image sensorresolution is kept the same. Detectors of higher quality (e.g., betterdigital cameras) have a large image sensor and a relatively large pixelsize for good image quality.

In some embodiments, a detector of the present invention has a pixelsize of 1 μm² or smaller; 2 μm² or smaller; 3 μm² or smaller; 4 μm² orsmaller; 5 μm² or smaller; 6 μm² or smaller; 7 μm² or smaller; 8 μm² orsmaller; 9 μm² or smaller; 10 μm² or smaller; 20 μm² or smaller; 30 μm²or smaller; 40 μm² or smaller; 50 μm² or smaller; 60 μm² or smaller; 70μm² or smaller; 80 μm² or smaller; 90 μm² or smaller; 100 μm² orsmaller; 200 μm² or smaller; 300 μm² or smaller; 400 μm² or smaller; 500μm² or smaller; 600 μm² or smaller; 700 μm² or smaller; 800 μm² orsmaller; 900 μm² or smaller; 1,000 μm² or smaller; 1,100 μm² or smaller;1,200 μm² or smaller; 1,300 μm² or smaller; 1,400 μm² or smaller; 1,500μm² or smaller; 1,600 μm² or smaller; 1,700 μm² or smaller; 1,800 μm² orsmaller; 1,900 μm² or smaller; 2,000 μm² or smaller; 2,100 μm² orsmaller; 2,200 μm² or smaller; 2,300 μm² or smaller; 2,400 μm² orsmaller; 2,500 μm² or smaller; 2,600 μm² or smaller; 2,700 μm² orsmaller; 2,800 μm² or smaller; 2,900 μm² or smaller; 3,000 μm² orsmaller; 3,100 μm² or smaller; 3,200 μm² or smaller; 3,300 μm² orsmaller; 3,400 μm² or smaller; 3,500 μm² or smaller; 3,600 μm² orsmaller; 3,700 μm² or smaller; 3,800 μm² or smaller; 3,900 μm² orsmaller; 4,000 μm² or smaller; 4,100 μm² or smaller; 4,200 μm² orsmaller; 4,300 μm² or smaller; 4,400 μm² or smaller; 4,500 μm² orsmaller; 4,600 μm² or smaller; 4,700 μm² or smaller; 4,800 μm² orsmaller; 4,900 μm² or smaller; 5,000 μm² or smaller; 5,100 μm² orsmaller; 5,200 μm² or smaller; 5,300 μm² or smaller; 5,400 μm² orsmaller; 5,500 μm² or smaller; 5,600 μm² or smaller; 5,700 μm² orsmaller; 5,800 μm² or smaller; 5,900 μm² or smaller; 6,000 μm² orsmaller; 6,500 μm² or smaller; 7,000 μm² or smaller; 7,500 μm² orsmaller; 8,000 μm² or smaller; 8,500 μm² or smaller; 9,000 μm² orsmaller; or 10,000 μm² or smaller. In some embodiments, the pixel sizeis larger than 10,000 μm², for example, up to 20,000 μm², 50,000 μm², or100,000 μm².

In some embodiments, exposure time to the detector can be adjusted tooptimize image quality and to facilitate the determination of a gradefor an optical quality of the gemstone, such as color or fluorescence.For example, the exposure time to a CCD detector can be 0.1 millisecond(ms) or longer, 0.2 ms or longer, 0.5 ms or longer, 0.8 ms or longer,1.0 ms or longer, 1.5 ms or longer, 2.0 ms or longer, 2.5 ms or longer,3.0 ms or longer, 3.5 ms or longer, 4.0 ms or longer, 4.5 ms or longer,5.0 ms or longer, 5.5 ms or longer, 6.0 ms or longer, 6.5 ms or longer,7.0 ms or longer, 7.5 ms or longer, 8.0 ms or longer, 8.5 ms or longer,9.0 ms or longer, 9.5 ms or longer, 10.0 ms or longer, or 15.0 ms orlonger. It is understood that the time of exposure can vary with respectto, for example, light source intensity.

FIGS. 7A and 7B illustrate images of a diamond in which the backgroundwhite color has been masked by black color. The opening of this mask (anoutline mask) corresponds to a full image of a diamond at a given imageview angle and a given image rotational angle. As illustrated in themethod of analysis section, such outline masks can be defined for eachimage to isolate the region of analysis and to extract measurements suchas width and height.

In another aspect, also provided herein is a data analysis unit,including both a hardware component (e.g., computer) and a softwarecomponent.

The data analysis unit stores, converts, analyzes, and processes of theimages collected by the optical unit. The computer unit controls variouscomponents of the system, for example, rotation and height adjustment ofthe platform, adjustment of the intensity and exposure time of theillumination source. The computer unit also controls the zoom, adjustsrelative position of the optic unit to the gemstone platform,

FIG. 8 illustrates an exemplary computer unit 800. In some embodiments,a computer unit 800 comprises a central processing unit 810, a powersource 812, a user interface 820, communications circuitry 816, a bus814, a non-volatile storage controller 826, an optional non-volatilestorage 828, and a memory 830.

Memory 830 may comprise volatile and non-volatile storage units, forexample random-access memory (RAM), read-only memory (ROM), flash memoryand the like. In some embodiments, memory 830 comprises high-speed RAMfor storing system control programs, data, and application programs,e.g., programs and data loaded from non-volatile storage 828. It will beappreciated that at any given time, all or a portion of any of themodules or data structures in memory 830 can, in fact, be stored inmemory 828.

User interface 820 may comprise one or more input devices 824, e.g.,keyboard, key pad, mouse, scroll wheel, and the like, and a display 822or other output device. A network interface card or other communicationcircuitry 816 may provide for connection to any wired or wirelesscommunications network. Internal bus 814 provides for interconnection ofthe aforementioned elements of the computer unit 800.

In some embodiments, operation of computer unit 800 is controlledprimarily by operating system 832, which is executed by centralprocessing unit 810. Operating system 832 can be stored in system memory830. In addition to operating system 832, a typical implementation ofsystem memory 830 may include a file system 834 for controlling accessto the various files and data structures used by the present invention,one or more application modules 836, and one or more databases or datamodules 852.

In some embodiments in accordance with the present invention,applications modules 836 may comprise one or more of the followingmodules described below and illustrated in FIG. 8.

Data processing application 838: In some embodiments in accordance withthe present invention, a data processing application 838 receives andprocesses optical measurements shared between the optical unit and dataanalysis unit. In some embodiments, data processing application 838utilizes an algorithm to determine the portion of the image thatcorresponds to the sample gemstone and eliminates the irrelevant digitaldata (e.g., edge defining and mask application). In some embodiments,data processing application 838 converts each pixel of the digitalimages into individual color components.

Content management tools 840: In some embodiments, content managementtools 840 are used to organize different forms of data 852 into multipledatabases 854, e.g., an image database 856, a processed image database858, a reference gemstone database 860, and an optional user passworddatabase 862. In some embodiments in accordance with the presentinvention, content management tools 840 are used to search and compareany of the databases hosted on computer unit 800. For example, images ofthe same sample gemstone taken at different time can be organized intothe same database. In addition, information concerning the samplegemstone can be used to organize the image data. For example, images ofdiamonds of the same cut may be organized into the same database. Inaddition, images of diamonds of the same source may be organized intothe same database.

The databases stored on the computer unit 800 comprise any form of datastorage system including, but not limited to, a flat file, a relationaldatabase (SQL), and an on-line analytical processing (OLAP) database(MDX and/or variants thereof). In some specific embodiments, thedatabases are hierarchical OLAP cubes. In some embodiments, thedatabases each have a star schema that is not stored as a cube but hasdimension tables that define hierarchy. Still further, in someembodiments, the databases have hierarchy that is not explicitly brokenout in the underlying database or database schema (e.g., dimensiontables are not hierarchically arranged).

In some embodiments, content management tools 840 utilize a clusteringmethod for determining grading characteristics.

System administration and monitoring tools 842: In some embodiments inaccordance with the present invention, the system administration andmonitoring tools 842 administer and monitor all applications and datafiles of computer unit 800. System administration and monitoring tools842 control which users, servers, or devices have access to computerunit 800. In some embodiments, security administration and monitoring isachieved by restricting data download or upload access from computerunit 800 such that the data is protected against malicious access. Insome embodiments, system administration and monitoring tools 842 usemore than one security measure to protect the data stored on computerunit 800. In some embodiments, a random rotational security system maybe applied to safeguard the data stored on remote computer unit 800.

Network application 846: In some embodiments, network applications 846connect computer unit 800 to network and thereby to any network devices.In some embodiments, a network application 846 receives data fromintermediary gateway servers or one or more remote data servers beforeit transfers the data to other application modules such as dataprocessing application 838, content management tools 840, and systemadministration and monitoring tools 842.

Computational and analytical tools 848: Computational and analyticaltools 848 can apply any available methods or algorithm to analyze andprocess images collected from a sample gemstone.

System adjustment tools 850: System adjustment tools 850 controls andmodifies configurations of various components of the system. Forexample, system adjustment tools 850 can switch between different masks,alter the size and shape of an adjustable mask, adjust zoom optics, setand modify exposure time, and etc.

Data module 852 and databases 854: In some embodiments, each of the datastructures stored on computer unit 800 is a single data structure. Inother embodiments, any or all such data structures may comprise aplurality of data structures (e.g., databases, files, and archives) thatmay or may not all be stored on computer unit 800. The one or more datamodules 852 may include any number of databases 852 organized intodifferent structures (or other forms of data structures) by contentmanagement tools 840.

In addition to the above-identified modules, various database 854 may bestored on computer unit 800 or a remote data server that is addressableby computer unit 800 (e.g., any remote data server that the computerunit can send information to and/or retrieve information from).Exemplary databases 854 include but are not limited to image database856, processed image database 858, reference gemstone database 860,optional member password dataset 862, and gemstone data 864.

Image database 856 is used to store images of gemstones before they areanalyzed. Processed image database 858 is used to store processedgemstone images. In some embodiments, processed image database 858 alsostored data that are converted from processed images. Examples ofconverted data include but are not limited to individual colorcomponents of pixels in an image, a two or three dimensional maprepresenting color distribution of the pixels in an image; computed L*,C*, a or b values of pixels in an image; average of L*, C*, a or bvalues for one or more images.

Reference gemstone database 860: Data of existing or known reference, ormaster gemstones (e.g., grade values or L*, C*, h values) are stored inreference gemstone database 860. In some embodiments, information of theknown reference, or master gemstones is used as standards fordetermining the grade values, or L*, C*, h values of an unknown gemstonesamples. The optical quality, such as color or fluorescence grade, hasalready been determined for the known reference, or master gemstones.For example, optical measurements of a sample diamond of brilliant cutare used to compute a value of L*, C*, h, which is then compared withthe values of L*, C*, h of a plurality of known reference, or masterdiamond of the same cut. The grade of the sample diamond will bedetermined by comparing their L*, C* and h with those of referencestones. In preferred embodiments, the reference gemstones are of thesame or similar size or weight as the sample gemstone.

Optional user password database 862: In some embodiments, an optionalpassword database 862 is provided. Password and other securityinformation relating to users of the present system can be created andstored on computer unit 800 where passwords of the users are stored andmanaged. In some embodiments, users are given the opportunity to choosesecurity settings.

In one aspect, provided herein are methods for system calibration, datacollection, data processing and analysis. For example, color digitalimages of gemstones are processed and computed to render one or morevalues for assessing and grading quality of cut gemstones such asdiamonds.

An exemplary process based on the apparatus and system disclosed hereinis outlined in FIG. 9A. One of skill in the art would understand thesteps provided are exemplary and can be applied in any order or used inany possible combination.

At step 910, system calibration is performed. For example, in order tohave reproducible results and cancel out the fluctuation of lightsource, white balance of an image capture component such as a colorcamera is adjusted. At this step, the pixel gains of individual colorcomponents (e.g., RGB) are adjusted such that the background image ofthe platform surface becomes white. Background adjustment is done with abare platform surface; i.e., the sample gemstone is not yet positionedon the platform surface. Preferably, the background adjustment is doneafter the light source has stabilized. In some embodiments, thebackground adjustment is done with a short time period before images ofa sample gemstone are collected. In some embodiments, the backgroundadjustment is done after the light source has stabilized and soon beforegemstone image collection. White background adjustment is performed whenthe top reflector module 60 is in closed configuration. The topreflector module is then opened and a user can place a sample gemstoneat the center of the platform surface. Care is taken such that theplatform surface, illumination and other conditions and settings in thesample chamber and for the optical unit remain the same before and afterthe sample gemstone is placed.

At step 920, a proportion or shape characteristic is determined based ona plurality of color images of the same sample gemstone. Here, eachimage includes a full image of the sample gemstone. Each image is takenat a unique image rotational angle and comprises a plurality of pixels.In some embodiments, the step of determining the proportion or shapecharacteristic is optional. For example, if by visual inspection, thesample gemstone has a perfect cut (e.g., a perfect round brilliant cutor RBC), there may be no need to determine the proportion or shapecharacteristic. A user can directly proceed to subsequent analysis.

A detailed exemplary process for determining the proportion or shapecharacteristic is outlined in FIG. 9B. First, the plurality of colorimages is collected at step 922. After the background adjustment iscompleted, a sample gemstone is placed on the platform surface; forexample, at or near the center of the platform surface but it is notrequired. In some embodiments, sample gemstones are placed at differentlocations on the platform surface. A plurality of color images of thegemstone are then taken at different image rotational angles. Inpreferred embodiments, the angular difference between consecutive colorimages remains constant throughout the collection of all images. Anyconfigurations disclosed herein (e.g., concerning image view angles andimage rotational angles) can be applied to the image collection process.For example, if the camera is set up to take 30 pictures per second andone full rotation of the sample platform takes 3 seconds, 90 images willbe collected after a full rotation. In some embodiments, platformsurface completes at least a full rotation with respect to the imagecapturing component. In some embodiments, the rotation is less than afull rotation. In some embodiments, the rotation is more than a fullrotation; for example, 1.2 full rotations or less, 1.5 full rotations orless, 1.8 full rotations or less, 2 full rotations or less, 5 rotations,or 10 full rotations or less.

At step 924, an outline mask is extracted for each image. Generally, anoutline mask corresponds to the physical area occupied by a samplegemstone, represented by the full image of the sample gemstone. FIGS. 7Aand 7B illustrate the differences for an image of the same diamond,before and after an outline mask is applied. As depicted in FIG. 7B, theoutline mask highlights and clearly defines the edges of the diamondsuch that parameters like width and height can be more easily measured.

There are many methods for edge detection, and most of them can begrouped into two categories, search-based and zero-crossing based. Thesearch-based methods detect edges by first computing a measure of edgestrength, usually a first-order derivative expression such as thegradient magnitude, and then searching for local directional maxima ofthe gradient magnitude using a computed estimate of the localorientation of the edge, usually the gradient direction. Thezero-crossing based methods search for zero crossings in a second-orderderivative expression computed from the image in order to find edges,usually the zero-crossings of the Laplacian or the zero-crossings of anon-linear differential expression.

The edge detection methods known to date mainly differ in the types ofsmoothing filters that are applied and the way the measures of edgestrength are computed. As many edge detection methods rely on thecomputation of image gradients, they also differ in the types of filtersused for computing gradient estimates in the x- and y-directions.

Here, any applicable method for extracting an outline mask can be used,including for example an edge determining filter in commerciallyavailable software products such as Photoshop™ and etc. Additionally,for example, a simple algorithm can be developed in which any continuousareas in an image with a color value matching the background white color(as previously calibrated) is defined as black. As a result, acontinuous black area will form the outline mask with an openingcorresponding to the full image of a sample gemstone.

At step 926, for each opening area corresponding to the full image of asample gemstone, values of geometrical parameters (e.g., the width andheight of the gemstone as illustrated in FIG. 7B) are determined.Outline masks are used for more accurate or automated measurements ofthe geometrical parameters. Essentially, the geometrical parameters aredetermined based on each outline mask, or more precisely, the opening ofeach outline mask. The measurements are taken for each image. After thisstep, a plurality set of measurement values are determined for theplurality of color images (or their corresponding outline masks),including, for example, a plurality of width measurements and aplurality of height measurements.

At step 928, one or more proportion or shape characteristics aredefined. For example, among the plurality of width measurements, themaximum width and the minimum width are identified. Width_(max) is themaximum width identified among the plurality of outline masks andWidth_(min) is the minimum width diamond width identified among theoutline masks. The characteristic, Width_(max)/Width_(min), is definedas the ratio of the maximum width versus the minimum width. Also forexample, an aspect ratio (defined as the ratio of height versus width:Height/Width) can be determined for each image (or outline mask). Thecharacteristic, Aspect_(max)/Aspect_(min), is defined as the ratio ofthe minimum aspect ratio versus the maximum aspect ratio. In someembodiments, average aspect ratios are also calculated and used as aproportion or shape characteristic. Another example of a shape orproportion characteristic is an average of aspect ratio; or averageHeight/Width. In some embodiments, the Width ratio (e.g.,Width_(max)/Width_(min)) and Aspect ratio (e.g.,Aspect_(max)/Aspect_(min)) of a sample gemstone, alone or incombinations, are used to classify the sample gemstone, for example, forthe purpose of selecting a region within the gemstone for further coloranalysis. In some embodiments, when the Width ratio (e.g.,Width_(max)/Width_(min)) is greater than an initial Width ratiothreshold value, the gemstones are significantly asymmetrical and willbe defined as fancy shape gemstones (FIG. 11A). In such embodiments, aWidth_(max)/Width_(min) threshold value is 1.05 or greater; 1.1 orgreater; 1.15 or greater; 1.2 or greater; 1.25 or greater, 1.3 orgreater; 1.35 or great, or 1.4 or greater.

In some embodiments, the non-fancy stones are subject to furtheranalysis. For example, when the Aspect ratio (e.g.,Aspect_(max)/Aspect_(min)) is smaller than an initial Aspect ratiothreshold value, the gemstones are flatter than a regular RBC and willalso be defined as fancy shape gemstones (FIG. 11A). In suchembodiments, a Aspect_(max)/Aspect_(min) threshold is less than 0.95;less than 0.9; less than 0.85; less than 0.8; less than 0.75; less than0.7; less than 0.65; or less than 0.6. In some embodiments, gemstonesthat are classified as regular gemstones after Aspect ratio analysis(e.g., RBC gemstones such as diamonds) are subject to furtherclassification; for example, using the average Aspect ratio as aparameter. When the average Aspect ratio of a gemstone (e.g., a diamond)is between a predetermined range, the gemstone will be classified asnormal RBC (FIG. 11A). When the average Aspect ratio of a gemstone(e.g., a diamond) is greater than the upper limit of the predeterminedrange, the gemstone is classified as having unusual shape (e.g., a highcrown or ice cream cone shaped diamond). Similarly, when the averageAspect ratio of a gemstone (e.g., a diamond) is smaller than the lowerlimit of the predetermined range, the gemstone is also classified ashaving unusual shape (e.g., a diamond with a shallow pavilion). In someembodiments, the upper limit of the predetermined range is between 0.6and 0.9; more preferably between 0.6 and 0.8 or between 0.7 and 0.85. Insome embodiments, the lower limit of the predetermined range is between0.4 and 0.7; more preferably between 0.5 and 0.7 or between 0.55 and0.65.

In some embodiments, gemstones that are classified as fancy stones(e.g., based on the exemplary algorithm in FIG. 11A) are furtherclassified. For example, a new Width ratio (e.g.,Width_(max)/Width_(min)) threshold is selected (FIG. 11B). Based on thisnew threshold value, the fancy gemstones are classified into two groups:those with a Width ratio higher than the new Width ratio threshold valueand those with a Width ratio lower than the new Width ratio thresholdvalue. The new Width ratio threshold value is higher than the previousWidth ratio threshold value; at for example, 1.2 or greater; 1.25 orgreater, 1.3 or greater; 1.35 or great, 1.4 or greater, 1.45 or greater,or 1.5 or greater.

In some embodiments, the further classified gemstones are subject tostill further classification; for example, by examining their Aspectratios (FIG. 11B). Gemstones with a Width ratio higher than the newWidth ratio threshold value are further classified based on theirminimum Aspect ratios (e.g., the minimum Height/Width ratio). Thesegemstones are classified into two groups using a first minimumHeight/Width ratio threshold value. Gemstones with a minimum Aspectratio at or higher than first minimum Height/Width ratio threshold valueare re-classified as normal stones. Gemstones with a minimum Aspectratio lower than first minimum Height/Width ratio threshold value arere-classified as shallow stones (FIG. 11B). In some embodiments, thefirst minimum Height/Width ratio threshold value is 0.6 or smaller; 0.55or smaller; 0.5 or smaller; 0.45 or smaller; 0.4 or smaller; 0.35 orsmaller; 0.3 or smaller; 0.25 or smaller; or 0.2 or smaller. Gemstoneswith a Width ratio lower than the new Width ratio threshold value arealso further classified based on their minimum Aspect ratios (e.g., theminimum Height/Width ratio) (FIG. 11B). These gemstones are classifiedinto two groups using a second minimum Height/Width ratio thresholdvalue. Gemstones with a minimum Aspect ratio at or higher than secondminimum Height/Width ratio threshold value are re-classified as normalstones. Gemstones with a minimum Aspect ratio lower than second minimumHeight/Width ratio threshold value are re-classified as shallow stones(FIG. 11B). In some embodiments, the second minimum Height/Width ratiothreshold value is 0.7 or smaller; 0.65 or smaller; 0.6 or smaller; 0.55or smaller; 0.5 or smaller; 0.45 or smaller; 0.4 or smaller; 0.35 orsmaller; 0.3 or smaller; 0.25 or smaller; or 0.2 or smaller.

Referring back to FIG. 9A, at step 930, depending on the values ofproportional characteristics such as a Width_(max)/Width_(min) ratio, aAspect_(max)/Aspect_(min) ratio, an average or minimum aspect ratio, adefined area will be selected within a full image of the samplegemstone. The defined area is selected by applying a virtual mask havingan open area that corresponds to a portion of the open area in thecorresponding outline mask. The information within the defined area willbe subject to further color analysis.

In some embodiments, a defined area or a virtual mask is calculated byproportionally shrinking the corresponding outline mask without changingthe weighed center. In some embodiments, a virtual mask is created byselected color area with specific range of color parameters. Forexample, only areas with an R, G, or B component having values in thespecified range will be included to form the virtual mask. In someembodiments, instead of ranges, predetermined threshold values can beused for selecting color areas; i.e., only areas with an R, G, or Bcomponent having values above or below the threshold will be included toform the virtual mask. In some embodiments, two color components areused in the evaluation. In some embodiments, all three color componentsare used in the evaluation. Other parameters that can be used indefining the virtual mask include but are not limited to L*, a*, b*, h,C, M, Y, K, and etc. It will be understood that each color parameter canbe used alone or in any combination with one or more other colorcomponents.

In some embodiments, a selected portion of the sample gemstone is usedto define the virtual mask. For example, for a diamond of roundbrilliant cut (RBC) but with a high crown (i.e., the ice cream cone typeRBC), only the top pavilion part is considered in further analysis byapplying a triangular virtual mask to only the top portion of thediamond.

In some embodiments, the defined area (e.g., the open area of a virtualmask) corresponds to the entire sample gemstone (e.g., outline mask). Insome embodiments, the defined area corresponds to a portion of theentire sample gemstone. In some embodiments, the defined areacorresponds to an upper portion of the sample gemstone. In someembodiments, the defined area corresponds to a middle portion of thesample gemstone. In some embodiments, the defined area corresponds to alower portion of the sample gemstone.

In some embodiments, the defined area corresponds to 20% or less of theentire gemstone, 25% or less of the entire gemstone, 30% or less of theentire gemstone, 35% or less of the entire gemstone, 40% or less of theentire gemstone, 45% or less of the entire gemstone, 50% or less of theentire gemstone, 55% or less of the entire gemstone, 60% or less of theentire gemstone, 65% or less of the entire gemstone, 70% or less of theentire gemstone, 75% or less of the entire gemstone, 80% or less of theentire gemstone, 85% or less of the entire gemstone, 90% or less of theentire gemstone, 95% or less of the entire gemstone, or 100% or less ofthe entire gemstone. For example, in some embodiments, the defined areain a normal RBC cut diamond corresponds to 100% of the entire gemstone.In some embodiments, the defined area in an RBC cut diamond with ashallow pavilion corresponds to only 50% of the entire gemstone. In someembodiments, the defined area in an RBC cut diamond with a high crowncorresponds to only the triangle part of the pavilion area. As describedabove, in some embodiments gemstones go through further analysis and arere-classified. In some embodiments, the defined area in a re-classifiednormal stones corresponds to 100% of the entire gemstone. In someembodiments, the defined area in a re-classified shallow stonecorresponds to only 30% of the entire gemstone.

The defined area can be in any shape. In some embodiments, the definedarea is a triangle. In some embodiments, the defined area is an oval, acircle, or a rectangle. In some embodiments, the defined area has anirregular shape, such as an area with four sides, five sides, and etc.In some embodiments, the defined area has a curved feature, such as anoval, a circle or an irregular curved shape. In some embodiments, thedefined area has a combination of straight-lined and curved features.For example, the defined area can be a triangle with a curved side.

At step 940, pixels within the defined area are subject to quantitativeanalysis. For example, each pixel can be analyzed to quantify the valuesof all color components in the particular pixel. The number of colorcomponent is determined by the algorithm according to which the pixel isencoded when the color image is first captured. In some embodiments, theimage is converted from its capturing color mode (e.g., CMYK) to adifferent color mode (e.g., RGB). Values for the individual colorcomponents are then converted to one or more parameters representing thecolor characteristic of each pixel. In some embodiments, RGB values areconverted to CIE (Commission Internationale de l'Eclairage orInternational Commission on Illumination) color space values such as(L*, a*, b*). An exemplary conversion process is depicted in FIG. 10.

At step 950, the conversion process is carried out for all pixels withina defined area in an image in order to calculate average values of theone or more parameters. The steps of 910-950 can be repeated for allimages in the plurality of color images. Eventually, average values ofthe one or more parameters (e.g., L*, a*, and b*) can be calculated foreach color component based on information from all images.

At step 960, one or more color scores are calculated based on the valuesof the one or more parameters. For example, in some embodiments, CIEcolor space values (e.g., L*, a*, and b*) are converted to additionalcolor score such as chroma (C*) and hue (h) values; e.g., based on thefollowing equations (FIG. 10):

$C*=\sqrt{{{{\left( a \right.{*)}}^{2} + \left( b \right.}{*)}}^{2}}$$h = {\tan^{- 1}\left( \frac{b*}{a*} \right)}$

In some embodiments, color images are analyzed using the standards(e.g., tables of color matching functions and illuminants as a functionof wavelength) published by CIE. A plot of the standard daylightilluminant with a correlated color temperature of 6500 K, D₆₅. Thisilluminant is represented here by the function H_(D65)(λ). The colormatching functions: x(λ), y(λ), z(λ) are used to calculate colorimetryparameters.

At step 970, values of color scores, e.g., L*, C*, h* are compared topreviously determined standard values to give a color grade to thesample gemstone. The previously determined standard values are obtainedusing the same or a similar process. For example, one or more sets ofsample stones, which share the same or similar proportion or shapecharacteristic and whose color grading values have been previouslydetermined, are used as the grading standards.

An example of computing color characteristics is as follows. As diamondis a transparent material, the sum of transmission spectrum T(λ) andreflection spectrum R(λ) is used in the calculation of the tristimulusvalues, X, Y and Z:XΣ _(λ=380) ⁷⁸⁰ H _(D65)(λ)(T(λ)+R(λ)) x (λ)YΣ _(λ=380) ⁷⁸⁰ H _(D65)(λ)(T(λ)+R(λ)) y (λ)ZΣ _(λ=380) ⁷⁸⁰ H _(D65)(λ)(T(λ)+R(λ)) z (λ)The chromaticity coordinates, x and y, are then defined as:

$x = \frac{X}{X + Y + Z}$ $y = \frac{Y}{X + Y + Z}$An attempt to achieve a “perceptually uniform” colour space is the CIE1976 colour space, otherwise known as the CIELAB colour space. Itsparameters are calculated from the tristimulus values as follows:lightness, L*=116(Y/Y_(W))^(1/3)−16

red-green parameter, a*=500[(X/X_(W))^(1/3)−(Y/Y_(W))^(1/3)]

and yellow-blue parameter, b*=200 [(Y/Y_(W))^(1/3)−(Z/Z_(W))^(1/3)],

where X_(W), Y_(W) and Z_(W) are the tristumulus values for the whitepoint corresponding to the chosen illuminant, in this case D65.

$X_{w} = {\sum\limits_{\lambda = 380}^{780}{{H_{D\; 65}(\lambda)}{\overset{\_}{x}(\lambda)}}}$$Y_{w} = {\sum\limits_{\lambda = 380}^{780}{{H_{D\; 65}(\lambda)}{\overset{\_}{y}(\lambda)}}}$$Z_{w} = {\sum\limits_{\lambda = 380}^{780}{{H_{D\; 65}(\lambda)}{\overset{\_}{z}(\lambda)}}}$

The saturation or chroma is expressed as: C*_(ab)=(a*²+b*²)^(1/3) andthe hue angle is expressed as: h_(ab)=tan⁻¹(b*/a*).

Sources are available for image/color conversion and transformation. Forexample the Open CV project hosted at the docs<dot>opencv<dot>org can beused to convert RGB values to CIE L, a, b values. In addition, the sameor similar resources allows conversion between RGB values andhue-saturation-value (HSV) values, between RGB values andhue-saturation-lightness (HSL) values, between RGB values and CIE Luvvalues in the Adams chromatic valence color space.

In another aspect, the methods and systems disclosed herein are used todetect or evaluate changes of color properties of a sample gemstone overtime. For example, the color of a gemstone may change over time. Also,the intensity of the color of a gemstone may change over time.

In such embodiments, multiple sets or pluralities of images (e.g., colorimages) are collected of a gemstone over a period of time. For example,using the system disclosed herein, each set of images is collectedautomatically over multiple image angles. There is no limitation as tohow much sets of image can be collected over time, for example, two ormore sets of images; three or more sets of images; four or more sets ofimages; five or more sets of images; six or more sets of images; sevenor more sets of images; eight or more sets of images; nine or more setsof images; 10 or more sets of images; 15 or more sets of images; 20 ormore sets of images; 30 or more sets of images; 50 or more sets ofimages; or 100 or more sets of images can be collected.

In some embodiments, all sets of images are collected of the samegemstone by applying the same system configuration; for example, usingthe same camera, same image angle, same reflector, same platform andetc.

Among the multiple sets of images, two consecutive sets of images areseparately for a time gap ranging from minutes to hours or even days,depending on the nature of the color change of the stone. The durationof the time gap is determined by how quickly color changes may takeplace in the sample stone. There is no limitation as to how long or howshort the time gap can be. For example, the time gap can be two minutesor shorter; five minutes or shorter; 10 minutes or shorter; 20 minutesor shorter; 30 minutes or shorter; 60 minutes or shorter; 2 hours orshorter; 5 hours or shorter; 12 hours or shorter; 24 hours or shorter; 2days or shorter; 5 days or shorter; or 10 days or shorter.

In some embodiments, calculations are done for each set of images toassign a color grade for the sample gemstone. Color grades from multiplesets of images are then compared to determine color change over time.

The present invention can be implemented as a computer system and/or acomputer program product that comprises a computer program mechanismembedded in a computer readable storage medium. Further, any of themethods of the present invention can be implemented in one or morecomputers or computer systems. Further still, any of the methods of thepresent invention can be implemented in one or more computer programproducts. Some embodiments of the present invention provide a computersystem or a computer program product that encodes or has instructionsfor performing any or all of the methods disclosed herein. Suchmethods/instructions can be stored on a CD-ROM, DVD, magnetic diskstorage product, or any other computer readable data or program storageproduct. Such methods can also be embedded in permanent storage, such asROM, one or more programmable chips, or one or more application specificintegrated circuits (ASICs). Such permanent storage can be localized ina server, 802.11 access point, 802.11 wireless bridge/station, repeater,router, mobile phone, or other electronic devices. Such methods encodedin the computer program product can also be distributed electronically,via the Internet or otherwise, by transmission of a computer data signal(in which the software modules are embedded) either digitally or on acarrier wave.

Some embodiments of the present invention provide a computer system or acomputer program product that contains any or all of the program modulesas disclosed herein. These program modules can be stored on a CD-ROM,DVD, magnetic disk storage product, or any other computer readable dataor program storage product. The program modules can also be embedded inpermanent storage, such as ROM, one or more programmable chips, or oneor more application specific integrated circuits (ASICs). Such permanentstorage can be localized in a server, 802.11 access point, 802.11wireless bridge/station, repeater, router, mobile phone, or otherelectronic devices. The software modules in the computer program productcan also be distributed electronically, via the Internet or otherwise,by transmission of a computer data signal (in which the software modulesare embedded) either digitally or on a carrier wave.

Having described the invention in detail, it will be apparent thatmodifications, variations, and equivalent embodiments are possiblewithout departing the scope of the invention defined in the appendedclaims. Furthermore, it should be appreciated that all examples in thepresent disclosure are provided as non-limiting examples.

EXAMPLES

The following non-limiting examples are provided to further illustrateembodiments of the invention disclosed herein. It should be appreciatedby those of skill in the art that the techniques disclosed in theexamples that follow represent approaches that have been found tofunction well in the practice of the invention, and thus can beconsidered to constitute examples of modes for its practice. However,those of skill in the art should, in light of the present disclosure,appreciate that many changes can be made in the specific embodimentsthat are disclosed and still obtain a like or similar result withoutdeparting from the spirit and scope of the invention.

Example 1 Instrument Color Grading of Cape Yellow Stones

FIGS. 12A and 12B depicts the grading results of 3 cape yellow stones.FIG. 12A shows that a mask with an opening matching the entire gemstonewas used in computing the color grade values for sample 1. Here the L,a, b, C, H values are calculated based on instrumental analysisdisclosed herein.

The grading results for samples 1 through 3 are summarized in the Tablein FIG. 12B. Here, the instrumental color grades for samples 1, 2, 3 areD, F and J, which matched the grades provided by visual gradingaccording to experience human grader(s).

The results shown here support that color grading by instrumentsdescribed herein is consistent with visual grading by human graders overa wide range of color quality.

Example 2 Instrument Color Grading of Stones of Unusual Colors

The table in FIG. 13 shows the results of color grading results ofstones of unusual or off colors. A gemstone is off color if the presenceof a particular color is weak or if there are multiple colors present.

Samples 4 through 7 include stones that are bluish, pinkish, brownishand greenish yellow. Once again, masks with an opening matching theentire gemstones were used in computing the color grade values forsample 4, sample 5, sample 6 and sample 7.

For bluish diamond (sample 4) both human grader and our instrumentprovided a color grade of E. For pinkish diamond (sample 5) both humangrader and our instrument provided a color grade of F. For brown diamond(sample 6) both human grader and our instrument provided a color gradeof Y/Z. For greenish yellow diamond (sample 7) both human grader and ourinstrument provided a color grade of F.

The result shown here supports that color grading by instrumentsdescribed herein is consistent with visual grading by human graders forlow color grade gemstone.

Example 3 Instrument Color Grading of Fancy Shape Stones

The table in FIG. 15 summarizes the color grading results of 3 exemplaryfancy shape stones. Again, masks with an opening matching the entiregemstones were used in computing the color grade values for sample 8,sample 9 and sample 10. Here, instrument grading once again providedcolor grades that are consistent with those provided by experience humangraders.

These examples show that gemstones that are initially classified asfancy shape stones can still be subject to a normal mask analysis; i.e.,using a mask having an opening that matches the entire gemstone (see,for example, FIG. 11B).

Example 4 Effects of Mask Adjustment Based on Proportion or Shape

This example illustrates the effects of mask adjustment on proper colorgrading. The grading results are summarized in the table in FIG. 15.Sample 11 is a stone with high depth. According to human grading, thecolor grade is J. When a mask with an opening corresponding to theentire gemstone area (100%) was used, instrumental color analysisprovided a color grade of L, significantly different from the humangrading result. However, when the mask open area was adjusted to atriangle that covered only a portion of the stone (for example, the topportion as illustrated in FIG. 11A), the color grade obtained frominstrument analysis became J, consistent with the result of humangrading.

Sample 12 is a stone with a low depth stone. According to human grading,the color grade is H. When a mask with an opening corresponding to theentire gemstone area (100%) was used, instrumental color analysisprovided a color grade of I, significantly different from the humangrading result. However, when the mask open area was adjusted to asmaller area that covered only a portion of the stone (for example, thetop 50% as illustrated in FIG. 11A), the color grade obtained frominstrument analysis became H, consistent with the result of humangrading.

The various methods and techniques described above provide a number ofways to carry out the invention. Of course, it is to be understood thatnot necessarily all objectives or advantages described may be achievedin accordance with any particular embodiment described herein. Thus, forexample, those skilled in the art will recognize that the methods can beperformed in a manner that achieves or optimizes one advantage or groupof advantages as taught herein without necessarily achieving otherobjectives or advantages as may be taught or suggested herein. A varietyof advantageous and disadvantageous alternatives are mentioned herein.It is to be understood that some preferred embodiments specificallyinclude one, another, or several advantageous features, while othersspecifically exclude one, another, or several disadvantageous features,while still others specifically mitigate a present disadvantageousfeature by inclusion of one, another, or several advantageous features.

Furthermore, the skilled artisan will recognize the applicability ofvarious features from different embodiments. Similarly, the variouselements, features and steps discussed above, as well as other knownequivalents for each such element, feature or step, can be mixed andmatched by one of ordinary skill in this art to perform methods inaccordance with principles described herein. Among the various elements,features, and steps some will be specifically included and othersspecifically excluded in diverse embodiments.

Although the invention has been disclosed in the context of certainembodiments and examples, it will be understood by those skilled in theart that the embodiments of the invention extend beyond the specificallydisclosed embodiments to other alternative embodiments and/or uses andmodifications and equivalents thereof.

Many variations and alternative elements have been disclosed inembodiments of the present invention. Still further variations andalternate elements will be apparent to one of skill in the art.

In some embodiments, the numbers expressing quantities of ingredients,properties such as molecular weight, reaction conditions, and so forth,used to describe and claim certain embodiments of the invention are tobe understood as being modified in some instances by the term “about.”Accordingly, in some embodiments, the numerical parameters set forth inthe written description and attached claims are approximations that canvary depending upon the desired properties sought to be obtained by aparticular embodiment. In some embodiments, the numerical parametersshould be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof some embodiments of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspracticable. The numerical values presented in some embodiments of theinvention may contain certain errors necessarily resulting from thestandard deviation found in their respective testing measurements.

In some embodiments, the terms “a” and “an” and “the” and similarreferences used in the context of describing a particular embodiment ofthe invention (especially in the context of certain of the followingclaims) can be construed to cover both the singular and the plural. Therecitation of ranges of values herein is merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g. “such as”) provided with respectto certain embodiments herein is intended merely to better illuminatethe invention and does not pose a limitation on the scope of theinvention otherwise claimed. No language in the specification should beconstrued as indicating any non-claimed element essential to thepractice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember can be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. One ormore members of a group can be included in, or deleted from, a group forreasons of convenience and/or patentability. When any such inclusion ordeletion occurs, the specification is herein deemed to contain the groupas modified thus fulfilling the written description of all Markushgroups used in the appended claims.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations on those preferred embodiments will become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Itis contemplated that skilled artisans can employ such variations asappropriate, and the invention can be practiced otherwise thanspecifically described herein. Accordingly, many embodiments of thisinvention include all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Furthermore, numerous references have been made to patents and printedpublications throughout this specification. Each of the above citedreferences and printed publications are herein individually incorporatedby reference in their entirety.

In closing, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that can be employed can be within thescope of the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention can be utilized inaccordance with the teachings herein. Accordingly, embodiments of thepresent invention are not limited to that precisely as shown anddescribed.

We claim:
 1. An apparatus for assessing a color characteristic of agemstone, comprising: an optically opaque platform, wherein the platformhas a surface configured for supporting a gemstone; adaylight-approximating light source at color temperature 6500 K, D65shaped to at least partially enclose the platform, wherein the lightsource is located at the same level as or below the platform and isdesigned to provide uniform diffused illumination to the gemstone on theplatform; a reflector having an inner surface that is at least partiallyspherical and comprises a reflective material, wherein the reflector atleast partially covers the light source and platform surface, andreflects illumination from the light source towards the gemstonepositioned on the platform surface; a camera and telecentric lens,wherein the camera and platform are configured to rotate relative toeach other and capture color images of the gemstone; and a computer witha processor and memory in communication with the camera, the computerconfigured to, receive multiple color images captured by the camera ofthe gemstone, wherein the received multiple color images are in Cyan,Magenta, Yellow, and Key (CMYK) color mode, convert each pixel in afirst area of a first received image of the multiple color images in theCMYK color mode images to Red Green Blue (RGB) color mode, convert thefirst converted RGB color mode for the first received image pixels toCommission Internationale de l′Elcairage (CIE) color space values of L*,a* and b*; convert each pixel in a second area of a second receivedimage of the multiple color images in the CMYK color mode images to RGBcolor mode, convert the second converted RGB color mode for the secondreceived image pixels to CIE color space values of L*, a* and b*,convert the CIE color space values of lightness L*, a* and b* to chroma(C*) and hue (h*) values, and compare the L*, C* and h* values topreviously determined standard values to determine a color grade for thegemstone.
 2. The apparatus of claim 1, wherein the camera is positionedat an angle 65 degrees or smaller as measured, relative to the platformsurface that supports the gemstone.
 3. The apparatus of claim 1, whereinthe telecentric lens comprises an object-space telecentric lens, or adouble telecentric lens.
 4. The apparatus of claim 1, wherein theplatform is configured to rotate about a rotational axis that isperpendicular to the surface of the platform where the gemstone issupported.
 5. The apparatus of claim 1 wherein the angle between thecamera and the platform surface is between approximately zero andapproximately 45 degrees.
 6. The apparatus of claim 1, wherein theplatform surface comprises a reflective or a diffuser material.
 7. Theapparatus of claim 1, wherein the daylight-approximating light source isconfigured as a ring light surrounding the platform surface.
 8. Theapparatus of claim 1, wherein the daylight-approximating light source isselected from the group consisting of one or more halogen lamps with acolor balancing filter, multiple light emitting diodes arranged in aring-like structure surrounding the platform surface, fluorescence lamp,Xe lamp, Tungsten lamp, metal halide lamp, laser-induced white light(LDLS), and combinations thereof.
 9. The apparatus of claim 1, whereinthe camera is selected from the group consisting of a color camera, aCCD camera, and one or more CMOS sensor arrays.
 10. The apparatus ofclaim 1, wherein the platform is made of a material selected from thegroup consisting of polytetrafluoroethylene (PTFE), fluoropolymer,barium sulfate, Gold, Magnesium Oxide, and combinations thereof.
 11. Theapparatus of claim 1 wherein the angle between the camera and theplatform surface is between approximately 10 degrees and approximately35 degrees.
 12. The apparatus of claim 1, wherein the platform surfacecomprises a reflective material.
 13. The apparatus of claim 1, whereinthe platform surface comprises a diffuse reflective material.
 14. Theapparatus of claim 1, wherein the platform surface comprises a whitediffuse reflective material.
 15. The apparatus of claim 1 wherein thecomputer is further configured to calculate an average color space valueof L*, a* or b* using the CIE color space values from the first receivedimage and the second received image.
 16. The apparatus of claim 15wherein the computer is further configured to determine a color scorefor the gemstone based on the calculated average color space value ofL*, a* or b*.